Description: Total testosterone: A hormone that causes male characteristics. The blood level is used by men to investigate abnormal sexual development and sexual dysfunction. Small amounts are produced in women's ovaries and levels are tested to evaluate virilization. A drop in testosterone levels can contribute to moodiness, weight gain, loss of muscle mass, and diminished libido.

Testosterone, Free (Dialysis): Measures the amount of testosterone not bound to any other chemicals in the blood and may be used to assist in the evaluation of testicular function when obesity, cirrhosis or thyroid disorders may alter testosterone binding proteins.

Both men and women can have health problems because of low or high levels of free testosterone. Women with high levels of free testosterone may have polycystic ovary syndrome (PCOS), a condition marked by infertility, lack of menstruation, acne, and excessive hair growth, especially on the face. Men with low levels of free testosterone can lose their sex drive, suffer bone loss, or become infertile.